3A.T.A. 100This is a universally accepted system for numbering aircraft maintenance documentation.The chapter number assigned to a specific system is the same, regardless of aircraft manufacturer.For example, ATA Chapter 21 is “Air Conditioning” on Boeings, Lockheeds, Airbus, etc.
7ComponentsA third number completes the ATA chapter reference, and is usually used to define a specific component in a subsystem.For example…27 00 FLIGHT CONTROL SYSTEM27 10 ROLL CONTROLAILERONThe 14 denotes the specific component in the aileron control system…in this case, the aileron itself
18As a part number is an identifier of a part design (independent of its instantiations), a serial number is a unique identifier of a particular instantiation of that part design. In other words, a part number identifies any particular (physical) part as being made to that one unique design; a serial number, when used, identifies a particular (physical) part (one physical instance)